Dr. Warren Phipps completed an Infectious Diseases fellowship and an MPH degree in Epidemiology at the University of Washington (UW), and currently holds a junior faculty position at UW and the Fred Hutchinson Cancer Research Center (FHCRC). This proposal describes a 5-year training program which will allow him to develop a career as an independent investigator in the field of Kaposi sarcoma (KS) and HIV-associated malignancies. The proposed studies attempt to address current limitations in KS staging and treatment by defining the relationship between human herpesvirus-8 (HHV-8) replication and KS treatment outcomes and evaluating the potential of HHV-8 to serve as a prognostic biomarker in persons with KS. This project builds on research I conducted during my fellowship studying HHV-8 replication and related lytic HHV-8 gene expression in a large prospective cohort of persons with and without KS at the Uganda Cancer Institute (UCI) in Kampala, Uganda. Preliminary data from these studies show that HHV-8 replication in the oropharynx and plasma of persons with KS is frequent, but that rates vary among individuals. Measurement of specific HHV-8 mRNA in KS lesions also shows that tumors display varying amounts of lytic gene transcripts, and that the quantity of lytic mRNA may be associated with different KS lesion types. Based on these observations, we hypothesize that differences in HHV-8 replication and lytic gene expression at oral, blood, and tissue sites contribute to the heterogeneous clinical manifestations of KS and variability in treatment response. To test this hypothesis, we propose to prospectively study 200 persons with HIV-associated KS initiating treatment with standard antiretroviral therapy (ART) and chemotherapy at the UCI. We will collect saliva, plasma, and KS lesion samples serially over the course of therapy up to one year, and we will quantify HHV-8 in specimens using polymerase chain reaction (PCR), including novel PCR assays to evaluate specific HHV-8 gene mRNA in tumors. We will then test whether levels of HHV-8 replication in these various anatomic sites are associated with clinical presentation or predict treatment response. This proposed study will advance our understanding of the biologic role of replicating HHV-8 and lytic gene expression in established KS disease and could make significant contributions to KS care. If we find that levels of HHV-8 replication predict treatment response or relapse, HHV-8 may be a useful biomarker and could improve current KS staging. If we find that HHV-8 replication is associated with disease presentation and response, our study would also provide a biologic rationale to pursue inhibition of HHV-8 as a KS treatment strategy in future studies. I will be supported throughout the K23 award by my mentors, Drs. Corey Casper, Larry Corey, and Anna Wald, who provide unparalleled expertise in herpesvirus virology and infection-related cancers. The proposed study will also receive laboratory support from internationally-recognized PCR experts at the UW Molecular Diagnostics Laboratory and biostatistical support from faculty at the UW and the Statistical Center for HIV/AIDS Research &Prevention (SCHARP) at FHCRC. Our group's collaboration with investigators at the UCI has also established the research infrastructure needed to complete the proposed studies in Uganda, including an experienced study staff, a specimen repository, and an on-site PCR lab. Along with the research study, my K23 proposal includes a carefully designed career development plan. My planned activities include didactic coursework in advance biostatistics, cancer epidemiology, and molecular virology. I will also pursue practical laboratory experiences in PCR methodology and cancer pathology to help me grow as a translational researcher. In order to participate in coursework and other career development activities in both Seattle and Uganda, I will split my time between the two sites during the award period, making 2-3 roundtrips annually. Through the proposed training and research program in this K23 award, I will be well-positioned to begin my next phase as an early-career independent investigator. In the near term, my goal is to build a productive research program in HHV-8 and KS in Uganda. Based of the findings of my K23 study, I anticipate conducting an HHV-8 biomarker validation study and a trial of anti-HHV-8 therapeutics, such as ganciclovir, in KS treatment. Ultimately, I hope to develop a research program aimed at integrating an understanding of virologic mechanisms of disease pathogenesis with the development of new approaches to KS treatment and prevention that will establish my career as an independent investigator in the field of HIV-associated malignancies.